But it shows there is a real appetite for serious apps on the iPad, a device that many have shrugged off as a toy. It also suggests that Microsoft and Google may want to make sure their office suites -- whether Web-based or apps -- work well on the iPad.

We multiplied that by the number of apps -- three -- and the $10 per app Apple charges, and get about $825,000 per week. (We are assuming that the three apps are roughly selling the same number of units, even though surely the top-ranked app of the three is selling more units than the third-ranked app.)

This obviously includes some significant assumptions: That the rate of iPad purchases and iWork app purchases remain the same. And this doesn't take seasonality, international expansion, international pricing, exchange rates, price adjustments, or competition from other office apps/sites into account.

Again, we're even assuming that the most popular app, Pages, sells the same number of copies as the lower-ranked apps, Numbers and Keynote, which obviously isn't the case. (They're probably not tremendously far apart, though.)